The former offices of a Dutch insurance company in The Hague will tomorrow morning see the climax of an extraordinary 14-year battle to seek redress for victims of the Balkan wars when the former Bosnian Serb warlord Radovan Karadzic goes on trial for genocide.

Poet and psychiatrist, convicted embezzler and new age guru, Karadzic is allegedly responsible for mass murder and the most barbaric behaviour in Europe since the Nazis. He is threatening to boycott the trial's opening at the International Criminal Tribunal for the former Yugoslavia.

Barring the arrest of his fugitive colleague, General Ratko Mladic, the Karadzic trial could mark the end of 15 years of the tribunal's work, a mixed record of achievements and failings in what has been a pioneering attempt to expand international justice to encompass crimes against humanity.

The trial is likely to open with a test of strength that will show who is calling the shots – the man accused of overseeing the attempt to wipe out the Muslims of eastern Bosnia or the panel of three judges hearing the case.

Karadzic insists on defending himself and, after 15 months in detention, maintains he is not ready, having had to plough through around one million pages of prosecution evidence. If the judges blink first, they will be repeating fateful mistakes, according to experienced observers, that handicapped previous big trials, awarding an early psychological victory to the man in the dock.

"Karadzic has learnt the lessons of [earlier] trials and may suspect a lack of confidence on the part of the judges to deal with obstructive tactics," said Sir Geoffrey Nice, the British QC who led the prosecution of the Serbian leader, Slobodan Milosevic, the first head of state to be tried for war crimes. "The judges let Milosevic defend himself. This allowed him to manipulate the system to slow the trial."

Mirko Klarin, who has been chronicling the workings of the court for more than a decade as director of the Sense news agency, believes that the judges have learnt their lessons from past fiascos, and that they may impose defence counsel on Karadzic to try to avoid the trial degenerating into a political circus.

"You had a disaster in the Milosevic case, and now you have a looming disaster in the Karadzic case," he said. "The biggest single mistake was letting the accused defend themselves."

For Emir Suljagic, a Muslim from eastern Bosnia who escaped the slaughter of more than 7,000 males by Karadzic's executioners in Srebrenica in July 1995, justice is coming very late, if at all, and leaves a bitter taste. He vested great hopes in the tribunal and is disillusioned. "I'm resigned to the fact that it has failed to provide justice. But that's hardly a surprise when it was created by the very organisation [the UN] that stood aside while genocide was carried out."

Karadzic may be finally on trial. But his creation, Republika Srpska, the Serbian Republic, is still entrenched in half of Bosnia, the product of genocide, ethnic cleansing and war crimes. "There were big failures, totally unacceptable," said Mirsad Tokaca, who heads a Sarajevo project that has carried out detailed investigations into the crimes of the war years.

Defenders counter that the tribunal has suffered from inflated expectations. It has no police force and cannot arrest suspects. Its resources are limited. It has been hobbled by incompetent staffing, a result of bureaucratic infighting at the UN and international politics.

But the achievements may in the longer term prove more enduring than the obvious defects. Two landmark verdicts stand out. In 2001 rape and sexual enslavement were established as crimes against humanity for the first time. And in 2004 the court found as legal fact that genocide – the gravest crime of all – was committed by the Serbs at Srebrenica in July 2005. The Karadzic trial will go further by trying to prove that genocide also took place in the whirlwind of Serbian violence in north-west Bosnia in the first months of the war in 1992.

"The tribunal may be imperfect, but it's still the best we have," said Klarin. "It established the principle that mass war crimes cannot go unpunished."

International courts dealing with war crimes in Rwanda, Sierra Leone or Lebanon may not have been possible without the lead taken by the Yugoslav tribunal, he added. And the International Criminal Court, the first permanent such institution, may be struggling, but would probably not exist without the Yugoslav precedent.

"It has established much new case law and has left an enormous legacy of evidence that would not have been available but for the trials. As a result, if you look at Africa, Sri Lanka or the Balkans themselves, you may find developing legal systems that would not have developed but for the work of the tribunal," said Nice.

The main impact may be deterrent. Compared with as recently as 20 years ago, political leaders everywhere are more likely to think twice, worried that their conduct could see them on international trial. Of the three big names, Mladic remains at large and Milosevic died in custody before a verdict. That leaves Karadzic and a trial crucial as to how the tribunal will be viewed.